Decouple the constant handler from the compiler so we can have more than one.

sdk/lib/_internal/compiler/implementation/compiler.dart

Index: sdk/lib/_internal/compiler/implementation/compiler.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compiler.dart b/sdk/lib/_internal/compiler/implementation/compiler.dart
index cbd205d4cc6757c487a70320587e106dd0adf790..418223895a6ac55875a62563a4e949f3d2e130b4 100644
--- a/sdk/lib/_internal/compiler/implementation/compiler.dart
+++ b/sdk/lib/_internal/compiler/implementation/compiler.dart
@@ -189,6 +189,7 @@ abstract class Compiler implements DiagnosticListener {
   ti.TypesTask typesTask;
   Backend backend;
   ConstantHandler constantHandler;
+  ConstantHandler metadataHandler;
   EnqueueTask enqueuer;
 
   static const SourceString MAIN = const SourceString('main');
@@ -248,6 +249,7 @@ abstract class Compiler implements DiagnosticListener {
                                          disallowUnsafeEval) :
         new dart_backend.DartBackend(this, strips);
     constantHandler = new ConstantHandler(this, backend.constantSystem);
+    metadataHandler = new ConstantHandler(this, backend.constantSystem);
     enqueuer = new EnqueueTask(this);
     tasks = [scanner, dietParser, parser, patchParser, libraryLoader,
              resolver, closureToClassMapper, checker, typesTask,
@@ -724,27 +726,6 @@ abstract class Compiler implements DiagnosticListener {
         () => resolver.computeFunctionType(element, signature));
   }
 
-  bool isLazilyInitialized(VariableElement element) {
-    Constant initialValue = compileVariable(element);
-    return initialValue == null;
-  }
-
-  /**
-   * Compiles compile-time constants. Never returns [:null:].
-   * If the initial value is not a compile-time constants reports an error.
-   */
-  Constant compileConstant(VariableElement element) {
-    return withCurrentElement(element, () {
-      return constantHandler.compileConstant(element);
-    });
-  }
-
-  Constant compileVariable(VariableElement element) {
-    return withCurrentElement(element, () {
-      return constantHandler.compileVariable(element);
-    });
-  }
-
   reportWarning(Node node, var message) {
     if (message is TypeWarning) {
       // TODO(ahe): Don't supress these warning when the type checker